Centrifuges are commonly used in medical and biological industries for separating and purifying materials of differing densities, such as viruses, bacteria, cells and proteins. A centrifuge includes a rotor and a container to support a sample undergoing centrifugation. The rotor is designed to hold the sample container while it spins up to tens of thousands of revolutions per minute. To avoid spillage, evaporation, or aerosoling of the sample, a cover is placed onto the container so as to provide a fluid-tight seal therebetween
During centrifugation, hydrostatic pressure within the container can compromise the seal integrity of the covered container. The hydrostatic pressure may force the sample to pass between the cover and the receptacle. Avoiding this type of leakage poses a great challenge when designing centrifuge sample containers. The prior art is replete with differing designs for sample-holding containers from which inspiration may be drawn to provide improved sample-holding centrifuge containers.
U.S. Pat. No. 718,643 to Lees et al. discloses a sealing-jar for preserving articles of food, FIG. 1, including a body of a receptacle (a), a recess (b), a cover (c), a flat flange (d), a circular down-turned rib (e), and a rubber gasket (f). A seal is achieved by the gasket (f) fitting around the cover (c), beneath the flange (d), so as to bear against the recess (b), but this seal is easily compromised by centrifugal forces.
Australian Pat. No. 4247/26 to Lucke et al. discloses an apparatus for sealing bottles and jars, FIGS. 1-3, containing a domed disc stopper 8 having a downwardly projecting wall 9 near its outer edge. The wall 9 is inclined to match the seating 7 at the top of a rigid neck 5 of a jar or bottle. A rigid cap 12 has internal screw-threads 6 that are designed to thread onto the neck 5. A resilient ring 10 fits into an annular groove in the face of the stopper, col. 3 lines 4-8. The resilient ring 10 seats against the neck 5 by the cap 12 pressing against the stopper 8.
U.S. Pat. No. 3,924,772 to Magnani et al. discloses an airtight container cap, FIGS. 1-3, containing a ring-nut 1 have an upper circular hole 2, a slot 3 on the side surface thereof and threads 4; a jar 7 with a threaded neck 6; glass stopper 8 having one groove 9 in the upper portion a second groove 10 in the lower portion and a shoulder 12; and a circular gasket 11. The circular gasket 11 is positioned within groove 10 of the glass stopper 8. The glass stopper 8 is then mounted inside of ring-nut 1 through hole 2. Ring-nut 1 is then threaded onto the neck 6 of a jar 7, forming a hermetic seal.
U.S. Pat. No. 4,844,273 to Hawkins et al. discloses a closure with enhanced sealing for a container, FIGS. 1-3, comprising a container neck lip 30 and a cap 18 having an inner skirt 24, a top 20 and a depending coaxial outer skirt 22. The outer skirt has internal threads 26 for engaging the complementary external threads 28 of the container neck. The inner skirt 24 has an interference fit with the inside of the container neck lip 30, thus, forming one element of the enhanced seal. A bead 32 projects inwardly from the depending skirt 22 and provides the second element of the enhanced seal by maintaining peripheral contact against the outside of the container neck lip 30. An o-ring 34 is positioned between the outer and inner skirts, 22 and 24 respectively, and becomes compressed between the top 20 and the container lip 30 to maintain a hermetic seal while the cap 18 is threaded on the container neck 12. The rigid inner skirt firmly presses against the inside of lip 30 and co-acts with the inwardly directed bead 32 maintaining peripheral contact with the outside lip 30, which helps to maintain the hermetic seal by retaining the o-ring 34 in its compressed state.
U.S. Pat. No. 5,291,783 to Hall discloses a tube 10 for use in a fixed angle centrifuge rotor having indicia 20 thereon indicating the level to which the tube may be filled with liquid without risk of spillage due to meniscus re-orientating.
U.S. Pat. No. 5,325,977 to Haynes et al. discloses a vented closure for a capillary tube assembly 10. The assembly 10 includes a capillary tube 12 having a bore extending therethrough and a cap 14 slidably mounted to on end of the tube 12. The cap 14 includes an enlarged head 16 and a substantially cylindrical body 18. One or more vent grooves 20 are formed into the body which allows air to escape when the cap 14 is in a first slidable position. The groove 20 typically extends parallel to the longitudinal axis of the cylindrical body 18.
U.S. Pat. No. 5,458,252 discloses an invertible pressure-responsive sealing cap I for attachment to a container 2 having a mouth 4 with an outwardly facing threaded portion 12. The mouth 4 has an inner cylindrical sealing surface 6. The cap 1 has a threaded portion 3 disposed on a cap skirt 5, with the threaded portion 3 facing inwardly toward a cap axis 7. A central dome portion 9 is symmetrically disposed about the cap axis 7 and extends outwardly therefrom, terminating in an annular portion 11. The dome portion 9 is initially concave and extends into the mouth 4 of the container 2. The interface of the dome portion 9 and the annular portion 11 define a first flexure area 17. A sealing portion 13 is disposed about the annular portion 11 defining a second flexure area 21 thereat. The sealing portion 13 includes an outwardly facing cylindrical surface 23. In operation, the cap 1 is mated to the container 2 and pressure build-up therein causes the dome portion 9 to flatten increasing the sealing force between the sealing surfaces 23 and 6. A drawback with the aforementioned containers is that the fluid-tight integrity of the seals is compromised by samples egressing therethrough during centrifugation, which has led to the development of seals which employ centrifugal force to drive a cap or plug against a container.
U.S. Pat Nos. 5,127,895 to R. Pawlovich; 5,395,001 to P. Moore; 5,361,922 to P. Moore et ale; 4,304,356 to S. Chulay et ale; 4,290,550 to S. Chulay et ale; 4,080,175 to S. Chulay et al.; and 4,076,170 to S. Chulay et al. ale, all assigned to the assignee of the present invention, disclose centrifuge containers which achieve a seal by having a cap or plug forced against a container under centrifugal force. In some of these patents, deformable o-rings are used as part of the seal mechanism. Tapered surfaces, annular ridges and annular grooves are all employed, as in U.S. Pat. No. 5,395,001, to achieve a sealed sample.
For centrifuge containers having large diameter openings, structural flexure of the sample containment assembly during a centrifugation run may permit air to pass from within the container. Thus, a container having a lid for sealing its open end will be subject to a small but significant negative air pressure as a result of the venting of air from the container. This presents operational difficulties to the lab technician who must contend with carefully removing the vacuum sealed lid without doing damage to it, and yet desires to rapidly perform the operation in order to minimize the down time between centrifugation runs.
What is needed is a capping assembly for a centrifuge container that is capable of maintaining a tight seal during a centrifugation run while at the same time is capable of easily releasing a vacuum that may develop within the container during the run. It is desirable that such a capping assembly be manufactured with minimum parts and easily maintained during its useful life.